1. Field of the Invention
The present invention relates to an image forming apparatus and a causal part determination method.
2. Description of Related Art
In general, an electrophotographic image forming apparatus (such as a printer, a copy machine, and a fax machine) is configured to irradiate (expose) a charged photoconductor with (to) laser light based on image data to form an electrostatic latent image on the surface of the photoconductor. The electrostatic latent image is then visualized by supplying toner from a developing device to the photoconductor (image carrier) on which the electrostatic latent image is formed, whereby a toner image is formed. Further, the toner image is directly or indirectly transferred to a sheet, followed by heating and pressurization, whereby an image is formed on the sheet.
A related technique has been proposed in which predetermined test images are produced under different four conditions and the concentrations of the test images are detected, to thereby determine the defective part from the results of the detection. The four conditions include a first condition in which AC voltage application to the charger and light exposure are performed, a second condition in which AC voltage application to the charger is performed but light exposure is not performed, a third condition in which AC voltage application to the charger is not performed but light exposure is performed, and a fourth condition in which AC voltage application to the charger and light exposure are not performed (see, for example, Japanese Patent Application Laid-Open No. 2009-63810).
In addition, a technique has been proposed in which a measured potential on the surface of a photoconductor or a measured concentration of toner attached on the surface of the photoconductor are compared with predetermined conditions, and on the basis of the comparison, the component of the image forming apparatus that requires adjustment is indicated (see, for example, Japanese Patent Application Laid-Open No. 06-262800).
In addition, the degree of image quality problem that is caused when an image is output is determined by using a recording head in which a plurality of recording devices are laid out, and on the basis of the degree thus determined, whether the cause exists in the recording head or in the other processes is determined (see, for example, Japanese Patent Application Laid-Open No. 2005-254491).
As described above, in the above-mentioned image forming apparatuses, an image formed on a sheet through various processes including charging, light exposure, development, transfer, fixing and so forth. Therefore, when an image defect is caused on a sheet on which an image is formed, it is not easy to determine the causal part of the image defect. In particular, the image defect of vertical streaks can be caused in any of the processes, and therefore when vertical streaks are formed, the user or serviceman has to inspect the operating states of the components used in the processes. Therefore, it has been difficult for the user and serviceman to promptly determine and deal with the causal part of the image defect.